Surface Roughness and Staining Susceptibility of Composite Resins after Finishing and Polishing. J Esthet Restor Dent 23:34–45, 2011 SANDRINE BITTENCOURT BERGER ALAN RODRIGO MUNIZ PALIALOL VANESSA CAVALLI AND MARCELO GIANNINI

Purpose The study aims to investigate the influence of filler size and finishing systems on the surface roughness and staining of three composite resins.

Introduction Addition of filler increases the strength, the toughness under strain, and the wear resistance of composites. The restorative composite resins are generally classified according to the size, content, and filler type. The filler size and shape can influence the surface roughness of dental composites.

The composite resin fillers appear to play an intrinsic role in how well a composite finishes. This study evaluated the surface roughness and staining susceptibility after finishing and polishing procedures of the three composite resins containing different filler particle sizes. The hypothesis tested was that both surface roughness and staining susceptibility are influenced by increasing filler size.

Materials

Methods The composites were inserted into the mold incrementally. Two layers were enough to fill the cavity and each increment was cured for 40 seconds. The second layer was covered with a polyester Mylar strip. Forty cylindrical specimens, 3-mm thick and 5-mm in diameter, of each resin composite were prepared in stainless steel split molds.

All specimens were stored in distilled water at 37°C for 24 hours. 40 specimens from each composite were randomly assigned to the four groups. The control group comprised the specimens that were not submitted to finishing and polishing procedures and kept untreated. The specimens were finished and polished by a single investigator, according to the manufacturer’s instructions.

All composite resins were treated with the three polishing agents: 1. Sof-Lex Finishing and polishing discs (3M ESPE) 2. FlexiDiscs (Cosmedent Inc.) and Enamelize 3. Enhance/PoGo After all specimens were polished, they were thoroughly rinsed with water and allowed to dry for 24 hours before measurement of the average surface roughness (Ra-µm)

A profilometer was used to measure the surface roughness of the specimens After the profilometric examination, three specimens per group were assigned for use in SEM observations The spectrophotometric analysis was carried out with seven specimens per group which were immersed separately in 1 mL of 2% methylene blue solution at 37°C.

After 24 hours, specimens were rinsed with distilled water for 30 seconds, airdried, and ground into powder. The resulting powder was placed into new tubes, which were filled with 4 mL of absolute alcohol. After 24 hours, the solutions were centrifuged and the supernatant was used to determine the absorbance in a spectrophotometer. The dye uptake of each specimen was expressed as µg dye/mL, where lower values indicate lower staining susceptibility.

Results

Discussion The size of filler particles is an important parameter that has been used to characterize the restorative material for purposes of clinical applications. The polishability of composite resins is influenced by the filler type, shape, and content.

In this current study, the filler size ranged from 0. 2 to 1 In this current study, the filler size ranged from 0.2 to 1.4 µm, and a clear relationship between filler size and composite surface roughness was not observed. The surfaces of the composites resemble that of the Mylar strip, with no differences in average surface roughness between them, depending on polishing methods and materials.

In this study, the surface roughness of the composites cured under the Mylar strip was similar. These results are attributed to the monomeric composition of the resin matrix and the type of fillers. Low staining susceptibility is generally related to a low water absorption rate, and hydrophobic resins or low resin content in the composition of the restorative material.

Cross-linked networks with unreacted pendant methacrylates that serve as plasticizers, which facilitate the absorption of dye. The increase in dye concentration means has been attributed to the porosity of some glass particles of the filler. Filtek Supreme Plus composes of more hydrophobic monomer so it has more stain resistant. Although there are nanofillers in Filtek Supreme Plus, they did not present a lower surface roughness than other materials after polishing.

Esthet-X composes of inorganic bariumalumino fluoroborosilicate glass (ranging from 0.02 to 2.5 microns) whereas Renamel composes of an average particle size of 0.02 to 0.04 microns. The size of the filler particles may be responsible for the differences in surface roughness between Esthet-X and Renamel Microfill after polished.

The surface polished with FlexiDiscs presents some pitting, which may be because of the plucking of the filler during the polishing, whereas polished with Sof-Lex shows scratches on the surface which can increase the surface roughness.

Renamel exhibited lower or similar surface roughness to the other composites. A rough surface was noted when the specimens were polished with Enhance + PoGo, whereas a smooth surface was obtained when Renamel Microfill was treated with FlexiDiscs + Enamelize and Sof-Lex polishing agents.

Esthet-X exhibited similar means of dye concentration to Renamel Microfill and control group due to they contain dental glasses as filler and conventional resin monomer But these were higher than that of Filtek Supreme Plus.

The development of an optimal surface polish can reduce the stain, biofilm accumulation, and gingival inflammation, minimizing the wear and improving the esthetics and the longevity of restorations. The polishing system from the same company as the composite resin should be used, as these showed good results in comparison with other polishers.

Conclusion The surface roughness and staining susceptibility are not solely influenced by filler size of the composite resins tested.

Clinical Significance Dentists should finish and polish composite resin with the polishing agent supplied by the same manufacturer. The smallest filler size does not necessarily result in a low surface roughness and staining susceptibility.

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